term_exists() WP 1.0

Check if Term exists.

Formerly is_term(), introduced in 2.3.0.

No Hooks.

Return

Mixed. Returns null if the term does not exist. Returns the term ID if no taxonomy is specified and the term ID exists. Returns an array of the term ID and the term taxonomy ID the taxonomy is specified and the pairing exists.

Usage

term_exists( $term, $taxonomy, $parent );

$term(int/string) (required)

The term to check. Accepts term ID, slug, or name.

$taxonomy(string)

The taxonomy name to use
Default: ''

$parent(int)

ID of parent term under which to confine the exists search.
Default: null

Code of term_exists: wp-includes/taxonomy.php ^{VER 4.9.8}

<?php
function term_exists( $term, $taxonomy = '', $parent = null ) {
	global $wpdb;

	$select = "SELECT term_id FROM $wpdb->terms as t WHERE ";
	$tax_select = "SELECT tt.term_id, tt.term_taxonomy_id FROM $wpdb->terms AS t INNER JOIN $wpdb->term_taxonomy as tt ON tt.term_id = t.term_id WHERE ";

	if ( is_int($term) ) {
		if ( 0 == $term )
			return 0;
		$where = 't.term_id = %d';
		if ( !empty($taxonomy) )
			return $wpdb->get_row( $wpdb->prepare( $tax_select . $where . " AND tt.taxonomy = %s", $term, $taxonomy ), ARRAY_A );
		else
			return $wpdb->get_var( $wpdb->prepare( $select . $where, $term ) );
	}

	$term = trim( wp_unslash( $term ) );
	$slug = sanitize_title( $term );

	$where = 't.slug = %s';
	$else_where = 't.name = %s';
	$where_fields = array($slug);
	$else_where_fields = array($term);
	$orderby = 'ORDER BY t.term_id ASC';
	$limit = 'LIMIT 1';
	if ( !empty($taxonomy) ) {
		if ( is_numeric( $parent ) ) {
			$parent = (int) $parent;
			$where_fields[] = $parent;
			$else_where_fields[] = $parent;
			$where .= ' AND tt.parent = %d';
			$else_where .= ' AND tt.parent = %d';
		}

		$where_fields[] = $taxonomy;
		$else_where_fields[] = $taxonomy;

		if ( $result = $wpdb->get_row( $wpdb->prepare("SELECT tt.term_id, tt.term_taxonomy_id FROM $wpdb->terms AS t INNER JOIN $wpdb->term_taxonomy as tt ON tt.term_id = t.term_id WHERE $where AND tt.taxonomy = %s $orderby $limit", $where_fields), ARRAY_A) )
			return $result;

		return $wpdb->get_row( $wpdb->prepare("SELECT tt.term_id, tt.term_taxonomy_id FROM $wpdb->terms AS t INNER JOIN $wpdb->term_taxonomy as tt ON tt.term_id = t.term_id WHERE $else_where AND tt.taxonomy = %s $orderby $limit", $else_where_fields), ARRAY_A);
	}

	if ( $result = $wpdb->get_var( $wpdb->prepare("SELECT term_id FROM $wpdb->terms as t WHERE $where $orderby $limit", $where_fields) ) )
		return $result;

	return $wpdb->get_var( $wpdb->prepare("SELECT term_id FROM $wpdb->terms as t WHERE $else_where $orderby $limit", $else_where_fields) );
}

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